Abstract The goal of this K01 Mentored Career Development Award is to investigate the role of FoxM1 and the contributions of PLK1 in the ?out-of-control? proliferation of human pulmonary artery smooth muscle cells (HPASMC) as research training towards independence for a PI. Vascular remodeling is a primary feature of pulmonary arterial hypertension (PAH) which is a fatal disease with very limited effective treatments. The pathology of the disease involves vascular cell proliferation resulting in thickening of the media and blockage of the vessel lumen. We discovered that the increased proliferative activities of the PAH HPASMC is associated with transcription factors, FoxM1 and p53, and cell cycle regulator polo-like kinase 1 (PLK1). To train towards independence the PI will pursue this research endeavor by testing the hypotheses that hyperplastic growth in PAH HPASMC is the consequence of upregulated FoxM1 and PLK1 activity. Aim 1 of this proposal is to investigate the roles of FoxM1 and PLK1 in the dysregulated proliferative behavior of HPASMC from PAH patients and mouse PASMC derived from mice exhibiting hypoxic PH. This approach will use siRNA knockdowns, lentivirus transduction of overexpressed wild-type or dominant negative forms of FoxM1 or PLK1 and implementation of targeted cell permeable peptides (CPP) in PASMC. Aim 2 will extend the studies on PASMC in culture into in vivo studies using mice exposed to hypoxia/SU5416 PH model. This will allow for an in vivo assessment of observations obtained from the human cells. In animal experiments the PI will use a strategy of a ?homing? peptide which is conjugated to a CPP, ensuring its delivery to target tissue. The PI will apply targeted CPP against molecules determined critical from Aim 1 and previous results to regulate or block dysfunctional smooth muscle proliferation. It is anticipated that the insights gained from this investigation will ultimately lead to new therapies that will ameliorate or reverse the hyperplastic smooth muscle pathology of the disease. The PI?s long term career goal is to become an independent investigator working on translational problems in pulmonary vascular disease. In the short term the PI will gain experience investigating problems involving gene and protein expression, intracellular cell signaling, animal model work and approaches to control diseases with targeted inhibitors such as cell permeable peptides. Training will involve the PI immersing in lung biology research through exploration of new physiological techniques via participation in ongoing animal experiments in his mentor?s lab, attending animal experiment workshops, participation in Pulmonary Division research seminars and journal clubs, presentations at large and specialized conferences related to lung biology research and graduate course work in pathobiology and introduction to clinical care research. Overall, this proposal will provide the candidate enough training in research aspects of lung biology and disease to develop into an independent investigator and compete for R01 grants.